x-gal plates for yeast

Hi!
Some years ago I remember I was growing yeast with LacZ constructs on
plates and was looking for blue colonies. I remember it was an easy and
quick way to identify various mutants that we were working on.
Now, I have to do something similar, but my yeast do not turn blue.
Does anyone have a working protocl for the x-gal in the plates? is there
something fancy about the protocol? I have lost my old method folder and
my memory is evidently failing me.
ThankX
Przemko